@rooeytoo & @JLeslie have it. The lead goose at the point of vthe vee breaks the static air. That goose works much harder to maintain the pace of flight than the geese flying in each trailing arm of the formation. And so they alternate lead position from time to time. Tel lead bird can fall back in the formation and catch its breath while a fresher one takes lead postion. Indeed, they are smart birds.

It is how they can all keep watch for predators together . It’s the same tactic that fighter pilots used back when aerial combat was strictly a visual affair. They flew their aircraft in a “V” formation for safety. Don’t think it has much to do with drafting the bird in front but I could be wrong.